Add a section listing companies that provide sponsored services to us.

Closes #2.

index.html

@@ -338,6 +338,57 @@ <h5 class="card-title text-white my-2">
                             </div>
                         </div>
                     </div>
+
+                    <hr />
+
+                    <h2 class="text-center mb-3">
+                        Benefactors
+                    </h2>
+
+                    <div class="row mb-3">
+                        <p class="card-text">
+                            The following companies are graciously providing their services to us for free as part of
+                            their open source sponsorship plans.
+                        </p>
+                    </div>
+
+                    <div class="row">
+                        <div class="col-md-4">
+                            <div class="card h-100">
+                                <div class="card-header text-center h-100">
+                                    <a href="https://www.gitbook.com"
+                                       title="GitBook">
+                                        <img class="card-img-top my-2"
+                                             style="width: 7rem;"
+                                             src="gitbook.svg"
+                                             alt="GitBook" />
+
+                                        <h5 class="card-title text-white my-2">
+                                            GitBook
+                                        </h5>
+                                    </a>
+                                </div>
+                            </div>
+                        </div>
+
+                        <div class="col-md-4">
+                            <div class="card h-100">
+                                <div class="card-header text-center h-100">
+                                    <a href="https://zulip.com"
+                                       title="Zulip">
+                                        <img class="card-img-top my-2"
+                                             style="width: 7rem;"
+                                             src="zulip.svg"
+                                             alt="Zulip" />
+
+                                        <h5 class="card-title text-white my-2">
+                                            Zulip
+                                        </h5>
+                                    </a>
+                                </div>
+                            </div>
+                        </div>
+                    </div>
                 </div>
             </main>